The objective of this paper is to investigate the relationship between the compositions of four typical infant formulae, the evolution of key quality characteristics during pneumatic conveying and the mechanical properties of individual agglomerates. Conveying experiments were conducted using a lab-scale rig. Four quality characteristics were measured before and after conveying: bulk density, volume mean diameter, wettability and percentage free fat. Relative breakages were calculated from particle size distributions. Uniaxial compression experiments were performed on individual agglomerates, giving forces and strains at failure and agglomerate stiffnesses. Coefficients of restitution of the agglomerates were obtained by video analyses of drop tests. The data indicate that bulk densities before conveying and the force and the strain of individual agglomerates at failure were related to the protein content. The force at failure and agglomerate stiffness were strongly correlated, and generally increased with increasing protein to fat ratio while the strain at failure decreased. (C) 2011 Elsevier Ltd. All rights reserved.